Add Fog rendering support

include/c3d/fog.h

@@ -0,0 +1,20 @@
+#pragma once
+#include "types.h"
+#include <math.h>
+
+typedef struct
+{
+	u32 data[128];
+} C3D_FogLut;
+
+static inline float FogLut_CalcZ(float depth, float near, float far)
+{
+	return far*near/(depth*(far-near)+near);
+}
+
+void FogLut_FromArray(C3D_FogLut* lut, const float data[256]);
+void FogLut_Exp(C3D_FogLut* lut, float density, float gradient, float near, float far);
+
+void C3D_FogGasMode(GPU_FOGMODE fogMode, GPU_GASMODE gasMode, bool zFlip);
+void C3D_FogColor(u32 color);
+void C3D_FogLutBind(C3D_FogLut* lut);

include/citro3d.h

@@ -24,6 +24,7 @@ extern "C" {
 #include "c3d/proctex.h"
 #include "c3d/light.h"
 #include "c3d/lightlut.h"
+#include "c3d/fog.h"
 
 #include "c3d/framebuffer.h"
 #include "c3d/renderbuffer.h" // Deprecated

source/base.c

@@ -59,6 +59,8 @@ static void C3Di_AptEventHook(APT_HookType hookType, C3D_UNUSED void* param)
 			ctx->fixedAttribDirty |= ctx->fixedAttribEverDirty;
 
 			C3D_LightEnv* env = ctx->lightEnv;
+			if (ctx->fogLut)
+				ctx->flags |= C3DiF_FogLut;
 			if (env)
 				C3Di_LightEnvDirty(env);
 			C3Di_ProcTexDirty(ctx);
@@ -115,6 +117,8 @@ bool C3D_Init(size_t cmdBufSize)
 	ctx->texShadow = BIT(0);
 	ctx->texEnvBuf = 0;
 	ctx->texEnvBufClr = 0xFFFFFFFF;
+	ctx->fogClr = 0;
+	ctx->fogLut = NULL;
 
 	for (i = 0; i < 3; i ++)
 		ctx->tex[i] = NULL;
@@ -240,8 +244,19 @@ void C3Di_UpdateContext(void)
 	if (ctx->flags & C3DiF_TexEnvBuf)
 	{
 		ctx->flags &= ~C3DiF_TexEnvBuf;
-		GPUCMD_AddMaskedWrite(GPUREG_TEXENV_UPDATE_BUFFER, 0x2, ctx->texEnvBuf);
+		GPUCMD_AddMaskedWrite(GPUREG_TEXENV_UPDATE_BUFFER, 0x7, ctx->texEnvBuf);
 		GPUCMD_AddWrite(GPUREG_TEXENV_BUFFER_COLOR, ctx->texEnvBufClr);
+		GPUCMD_AddWrite(GPUREG_FOG_COLOR, ctx->fogClr);
+	}
+
+	if (ctx->flags & C3DiF_FogLut)
+	{
+		ctx->flags &= ~C3DiF_FogLut;
+		if (ctx->fogLut)
+		{
+			GPUCMD_AddWrite(GPUREG_FOG_LUT_INDEX, 0);
+			GPUCMD_AddWrites(GPUREG_FOG_LUT_DATA0, ctx->fogLut->data, 128);
+		}
 	}
 
 	if (ctx->flags & C3DiF_TexEnvAll)

source/fog.c

@@ -0,0 +1,82 @@
+#include "internal.h"
+
+void FogLut_FromArray(C3D_FogLut* lut, const float data[256])
+{
+	int i;
+	for (i = 0; i < 128; i ++)
+	{
+		float in = data[i], diff = data[i+128];
+
+		u32 val = 0;
+		if (in > 0.0f)
+		{
+			in *= 0x800;
+			val = (in < 0x800) ? (u32)in : 0x7FF;
+		}
+
+		u32 val2 = 0;
+		if (diff != 0.0f)
+		{
+			diff *= 0x800;
+			if (diff < -0x1000) diff = -0x1000;
+			else if (diff > 0xFFF) diff = 0xFFF;
+			val2 = (s32)diff & 0x1FFF;
+		}
+
+		lut->data[i] = val2 | (val << 13);
+	}
+}
+
+void FogLut_Exp(C3D_FogLut* lut, float density, float gradient, float near, float far)
+{
+	int i;
+	float data[256];
+	for (i = 0; i <= 128; i ++)
+	{
+		float x = FogLut_CalcZ(i/128.0f, near, far);
+		float val = expf(-powf(density*x, gradient));
+		if (i < 128)
+			data[i] = val;
+		if (i > 0)
+			data[i+127] = val-data[i-1];
+	}
+	FogLut_FromArray(lut, data);
+}
+
+void C3D_FogGasMode(GPU_FOGMODE fogMode, GPU_GASMODE gasMode, bool zFlip)
+{
+	C3D_Context* ctx = C3Di_GetContext();
+
+	if (!(ctx->flags & C3DiF_Active))
+		return;
+
+	ctx->flags |= C3DiF_TexEnvBuf;
+	ctx->texEnvBuf &= ~0x100FF;
+	ctx->texEnvBuf |= (fogMode&7) | ((gasMode&1)<<3) | (zFlip ? BIT(16) : 0);
+}
+
+void C3D_FogColor(u32 color)
+{
+	C3D_Context* ctx = C3Di_GetContext();
+
+	if (!(ctx->flags & C3DiF_Active))
+		return;
+
+	ctx->flags |= C3DiF_TexEnvBuf;
+	ctx->fogClr = color;
+}
+
+void C3D_FogLutBind(C3D_FogLut* lut)
+{
+	C3D_Context* ctx = C3Di_GetContext();
+
+	if (!(ctx->flags & C3DiF_Active))
+		return;
+
+	if (lut)
+	{
+		ctx->flags |= C3DiF_FogLut;
+		ctx->fogLut = lut;
+	} else
+		ctx->flags &= ~C3DiF_FogLut;
+}

source/internal.h

@@ -5,6 +5,7 @@
 #include <c3d/light.h>
 #include <c3d/framebuffer.h>
 #include <c3d/texenv.h>
+#include <c3d/fog.h>
 
 #define C3D_UNUSED __attribute__((unused))
 
@@ -48,6 +49,8 @@ typedef struct
 	C3D_TexEnv texEnv[6];
 
 	u32 texEnvBuf, texEnvBufClr;
+	u32 fogClr;
+	C3D_FogLut* fogLut;
 
 	C3D_ProcTex* procTex;
 	C3D_ProcTexLut* procTexLut[3];
@@ -79,6 +82,7 @@ enum
 	C3DiF_TexStatus = BIT(14),
 	C3DiF_ProcTex = BIT(15),
 	C3DiF_ProcTexColorLut = BIT(16),
+	C3DiF_FogLut = BIT(17),
 
 #define C3DiF_ProcTexLut(n) BIT(20+(n))
 	C3DiF_ProcTexLutAll = 7 << 20,